Reduction of griseofulvin



United States Patent 3,392,175 REDUCTION OF GRISEOFULVIN Jack Lassman, Ilford, England, assignor to Glaxo Group Limited, a limited corporation of England No Drawing. Filed Feb. 10, 1961, Ser. No. 88,293

Claims priority, application Great Britain, Feb. 12, 1960,

5,178/ 60 3 Claims. (Cl. 260-346.2)

ABSTRACT OF THE DISCLOSURE A process for preparing a derivative of griseofulvin by metal hydride reduction. The products are useful as antifungals.

This invention is concerned with the preparation of derivatives of griseofulvin having interesting biological properties.

The derivatives of griseofulvin prepared according to the invention have the general formula I 00 on H I R on I O CH: 01 I Where R and R are alkyl groups, and R is an alkyl or alkenyl group.

The compounds of the above general formula may also be substituted in the 3-position e.g. by halogen atoms, alkyl groups etc.

The compounds prepared according to the invention have in vivo biological activity akin to that of the corresponding 4-oxo compounds, but in general possess little antifungal action in vitro. Thus some of the compounds are particularly useful for internal administration to man and animals for the treatment of various fungal conditions, particularly those fungal conditions for which griseofulvin is known to be useful. The compound of Formula I, however, possess the advantage of a greater water solubility than the corresponding 4'-keto compounds, thus facilitating the preparation of various pharmaceutical formulations. The compounds are also well absorbed by virtue of their solubility.

The compounds prepared according to the invention are also useful for the preparation of various other analogues of griseofulvin and can, for example, be esterified with organic or inorganic acids or etherified.

Preferred compounds prepared according to the invention are those in which R is a methyl group, R is a lower alkyl group i.e. an alkyl group having 1-4 carbon atoms, e.g. a methyl, ethyl, propyl or isopropyl group, and R is a lower alkyl group e.g. methyl. One compound of particular interest is 7-chlor0-4'-hydroxy-6-methyl-4,6,2- trimethoxygris-2-en-3-one which has in vivo substantially the antifungal activity of griseofulvin itself but is substantially more water soluble.

Compounds of Formula I in which R R and R are alkyl groups are new compounds except where R R and R are methyl groups. The invention thus further includes compounds of Formula I in which R R and R are lower alkyl groups, i.e. having 1-4 carbon atoms except that where R and R are methyl groups R is an alkyl group having 2-4 carbon atoms.

The invention further includes esters of the compounds of Formula I with organic and inorganic acids, e.g. the acetates. Partial esters of the compounds with dicarboxylic and polycarboxylic acids e.g. the hemisuccinate or hemiphthalate are of especial interest in that they enable water soluble salts such as the alkali metal or ammonium salts to be prepared, for example the sodium salts. Other esters of compounds of Formula I also have better solubility characteristics than the corresponding 4-keto compounds, and thus, for example, the acetates are generally more soluble in oils such as arachis oil.

For administration to man or animals the compounds prepared according to the invention can be compounded with a pharmaceutical carrier or diluent, the nature of which, as will be clear, will depend upon the type of presentation required. For example, the compounds may be presented for oral administration in solid form, for example as tablets, pills, capsules, granules, powders, etc. Oral liquid preparations of aqueous or oily nature may also be prepared, including such flavouring, sweetening, dispersing and/or colouring agents as may be required.

The compounds may also be presented in suppository form together with a suppository base.

For injection the compounds may be dissolved or dispersed in a sterile parenterally acceptable liquid which may be of an oily or aqueous nature.

For administration to animals the new compounds may be admixed with an animal feed or presented as a concentrate (together with an inert diluent) for admixture to an animal feed, or as a drench.

For use in agriculture and horticulture the new compounds can be formulated in any desired manner e.g. as emulsions, dispersions or solutions in a suitable carrier or as wettable powders or dusts, in conjunction with suitable wetting or dispersing agents, sticking agents, diluents, etc.

According to the invention the compounds of Formula I are prepared by the reduction of compounds of the general formula.

Cl II with a metal hydride reducing agent. Suitable reducing agents are the alkali metal and alkaline earth metal hydrides, the complex alkali metal and alkaline earth metal borohydrides and aluminium hydrides. Examples of such substances which are very satisfactory are sodium borohydride, potassium borohydride, calcium borohydride and lithium aluminium hydride.

The reaction is conveniently carried out in the presence of an inert solvent medium, the nature of which will, of course, depend upon the reducing agent used. In the case of borohydrides the solvent medium may in general be aqueous or non-aqueous, suitable solvent media being for example, dioxan, aqueous dioxan, tetrahydrofuran, aqueous tetrahydrofuran, methanol, aqueous methanol, ethanol, aqueous ethanol etc. However more reactive hydrides, e.g. the aluminium hydrides, in general require the use of non-hydroxylic solvents, e.g. anhydrous ether, tetrahydrofuran and dioxan. The reaction may be conveniently carried out at temperatures of from 0 to C.

Where more reactive hydrides are used such as lithium aluminium hydride care should be taken to avoid reduction taking place at other parts of the molecule and for example excess of reagent and forcing conditions should be avoided.

The desired product may be recovered from the reaction medium as convenient, for example, Where the reaction medium is of an aqueous nature, by addition of aqueous acid, dilution with water, followed by separation of the precipitated material and recrystallization, for example with benzene. The starting materials used Example 1.7-chloro-4'-hydroxy-6'-methyl-4,6,2'-trimethoxygris-2-ene-3-one Griseofulvin (7.06 g.; 0.02 mole) was dissolved in dioxan (180 ml.) and diluted with water (45 ml.). A solution of potassium borohydride (2.16 g.; 0.04 mole; 2 equivs.) in water (15 ml.) was added dropwise with swirling to the dioxan solution, which was kept at room temperature for 3 hours with occasional shaking.

The excess hydride was decomposed with dilute acetic acid (vigorous efi'ervescence) and the solution poured into water (3 litres) with stirring. After standing overnight at the precipitate was collected, washed with water and dried over P 0 in vacuo, 4.39 g., M.P. 124 128 C., softening at 104 C. Three recrystallisations from benzene gave 2.40 g. M.P. 152-155 C., [a] =+119.2 (c. 1 in acetone). (Found: C, 59.57; H, 5.67; Cl, 9.39. C H O CL1/4C H requires C, 59.34; H, 5.52; Cl, 9.47%.) The infra-red spectrum showed the presence of a little benzene, hydroxyl and one ketone group (1700 cm. The ultra-violet spectrum in ethanol had A at 237 m (e=l5,900), 288 my. (e=22,700), 322 m, (e=5,100) and )t 250 mu (6: 1,300).

Example 2.Preparation of 4'-acetoxy-7-chloro- 2':4:6-trimethoxy-6-methylgris-2-en-3-one Acetic anhydride (0.41 g.; 0.38 ml.; 0.004 mole) was added to a solution of 7-chloro-4'-hydroxy-2:4:6-trimethoxy-6-methylgris-2-ene-3-one (0.70 g.; 0.002 mole) in dry pyridine ml.), which was then left at room temperature for 72 hours. After pouring this solution into water (130 ml.), a white solid precipitated and was filtered oif, after chilling, washed well with water and dried, 0.68 g. M.P. 205.5207.5. Crystallisation from aqueous acetone afforded 4-acetoxy-7-chloro-2':4: 6-trimethoxy-6-methylgris-2'-en-3-one 0.51 g. M.P. 201-202 [a] -=-|95 (c.=1, acetone). Infra-red spectrum showed no hydroxyl absorption and bands at 1724, 1235 cm.- (acetate) and 1708 cm.- (ketone). Ultra-violet absorption maxima in ethanol at The analytical specimen was dried at 90/15 mm. (Found: C, 57.50; H, 5.13; Cl, 9.00; OMe, 23.08. C H O Cl requires C, 57.50; H, 5.33; Cl, 8.94; OMe, 23.50%).

Example 3.4-n-butoxy-7-chloro-4-hydroxy-6,2-

dimethoxy-6'-methylgris-2'-en-3-one 4 n butoxy-7-chloro-6,2-dimethoxy-6'-methylgris- I 2'-en-3,4'-dione (2.0 g.) was dissolved in dioxan (50 ml.)

and water (10 ml.) and stirred at room temperature. Potassium borohydride (1.5 g.) in water (10 ml.) was added dropwise during 30 minutes and the mixture was stirred for 3 hours and allowed to stand overnight. Excess borohydride was destroyed by the cautious addition of acetic acid and the mixture was poured into Water (250 ml.). After cooling for 30 minutes in the refrigerator, the crude 4-n-butoxy-7chloro-4'-hydroxy-6,2'-dimethoxy-6'-methylgris-2'-en-3-one was collected by filtration, washed with water and dried in vacuo at 60. Recrystallisation from ethanol gave the pure sample (1.8 gr., 90%), M.P. 1523" (loss of solvent at 110-114), [a] +1l3 (c. 1.008, acetone, microtube) (Found: C, 59.9; H, 6.4; Cl, 8.9. C H O CL1/4H O requires C, 59.9; H, 6.4; Cl, 8.9%

EXAMPLE 4 In a similar manner to Example 1, 7-chloro-6,2-dimethoxy-6-methyl-4-n-propoxyg-ris-2-en-3,4 dione was reduced to 7-chloro-4-hydroxy-6,-2'-dimethoxy-6'-methyl- 4-n-propoxygris-2'-en-3-one in good yield. The compound crystallised from aqueous alcohol, M.P. 175 7 [a] +l22.5 (c. 1.2, acetone, micro-tube) (Found: C, 59.2; H, 6.1; Cl, 9.20. C H O Cl requiresC, 59.6;"H, 6.1; Cl, 9.3%). a

Example 5 In similar manner to Example 1 6-n-butoxy-7-chloro- 4,2'-dimethoxy-6-methylgris-2-en-3,4-dione was reduced to 6 n butoxy 7-chloro-4'-hydroxy-4,2-dimethoxy-6- methylgris-2'-en-3-one in good yield. The compound crystallised from aqueous ethanol, M.P. 1589, [a], +108 (c. 0.915, acetone). Found: C, 57.6; H, 6.6;'Cl, 8.6. C2 H250 ClH2O I'eqliil' C, H, CI, 8.6%.

Example 6.7-chloro-4'-hydroxy-4,6,2-trimethoxy- 6'-methylgris-2'-en-3-one hemisuccinate 7 chloro-4'-hydroxy-4,6,2'-trimethoxy-6-methylgris- 2'-en-3-one (5 g.) and succinic anhydride (5 g.) in pyridine (50 ml.) were warmed at for 3 hrs. The brown reaction mixture was poured into water (500 ml.) and the cloudy solution was filtered through a kieselghur pad. The filtrate was acidified to pH 4 giving a sticky brown solid which was extracted into ethyl acetate (2)( 75 ml.). The combined extracts were washed with water and dried over magnesium sulphate. Evaporation of the solvent gave a foam (4.8 g.) which was dissolved in ethyl acetate and washed with a solution of sodium carbonate (0.5 g.) in water (50 ml.). The aqueous layer was freed of ethyl acetate in vacuo at room temperature. Ether (25 ml.) was added and the vigorously stirred mixture was neutralised with N/ 10 hydrochloric acid. The white granular precipitate was collected and dried (2.1 g.); crystallisation from ethanol gave the ethanol solvate of 7-chloro- 4 hydroxy 4,6,2'-trimethoxy-6-methylgris-2'-en-3-one hemisuccinate, M.P. l07-1l0, [e1 +83 (c. 0.72, N- sodium carbonate). Found: C, 55.25; H, 5.9; Cl, 7.2. C H ClO -C H OH requires C, 55.1; H, 5.8; Cl, 7.1%;

Example 7.-4'-benzoyloxy-7-chloro-4,6,2'-trimethoxy- 6'-methylgris-2-en-3-one The benzoylation of the product of Example 1 by treatment with benzoyl chloride in dry pyridine at room temperature for 20 hours yielded the desired benzoate. M.P. 186 [aJ 88 after recrystallisation from benzene-light petroleum (B.P. 60-80).

The following examples illustrate pharmaceutical formulations of the product of Example 1 (termed for con- Aerosil compositum, and most of the starch. The remaining starch is used in the form of starch paste as a granulating medium. The tablets may be prepared in the conventional manner, the magnesium stearate being added to the dried granules, before compression, as a lubricating medium. a r

The tablets may be uncoated, or sugar-coated, orthey may be compressed coated, using aninert material, such as lactose or sugar for the outer coating. The'tablets may also be film coated.

Example 9.--Oral aqueous suspension Griseofulvol percent w./v 5 Sorbitol syrup 70% percent v./v 50 Sodium cyclamate percent w./v 0.5 Saccharin sodium do 0.2 Methyl ester of p-hydroxy benzoate do 0.02 Propyl ester of p-hydroxy benzoate do 0.015 Methyl cellulose percent 1.5 Lecithin do 0.1 Peppermint oil B.P. percent v./v 0.05 Water to 100.00

Dissolve the preservatives in 95% (approximately) of the available water, heated to 9095 C. Disperse the methyl cellulose in the hot solution, allow to cool overnight and homogenise the mixture.

Adsorb the peppermint oil onto the griseofulvin analogue (finely milled), and blend in the sweetening agents and lecithin. Make a thick slurry of the powders with some of the sorbitol syrup and refine the mixture through a colloid mill set at a very fine gap. Use the remaining sorbitol syrup to rinse the mill and add the rinsings to the refined slurry. Blend the methyl cellulose mixture and slurry together and adjust to the intended volume with water. Mix well, avoiding air entrainment.

Example 10.Capsules for oral use Mg. The acetate of griseofulvol 250 Glycine 70 Blend the powders, both finely milled and fill 320 mg. of the dry mix into gelatin capsules.

Example 11.Suppositories Mg. Griseofulvol 250 Massupol suppository base to one gram.

Warm the suppository base to a temperature not exceeding 45 C. Slowly sprinkle in the griseofulvol (finely milled). Mix, without aeration to obtain even dispersion and allow the mix to cool slowly. Maintain at 39 to 40 C. and pour directly into chilled moulds.

Example l2.Ointmentgreasy base Percent Acetate of griseofulvol Liquid paraffin B.P. Wool alcohols ointment B.P. 75

Slurry the finely milled powder with the liquid paraffin and add the slurry to the wool alcohols ointment, previously warmed to 50 C. Stir to mix, until the ointment begins to congeal and refine by passing the preparation through an ointment mill.

Melt together the cetostearyl alcohol, cetomacragol, white soft parafiin and liquid paraffin and maintain at 50 C. Sprinkle the finely milled griseofulvol into the mix and disperse well by means of a mechanical stirrer. Dissolve the chlorocresol in the calculated weight of water by heating to C. with vigorous stirring. Slowly add the oil mixture at 50 C. to the chlorocresol solution at 55 C., using a mechanical stirrer fitted with radial flowhead to effect emulsification. Apply external cooling to the mixing vessel until the cream begins to congeal. Finally pass the cream through an ointment mill.

Example l4.Freeze-dried ampoules for parenteral use Mg. Disodium salt of the hemisuccinate of griseofulvol 200 Prepare a 10% solution of the salt by dissolving in water for injection at a temperature below 10 C. Sterilise as quickly as possible by filtration through a sinte-red glass filter; distribute 2.0 cc. of the solution into sterile ampoules and freeze the ampoules under aseptic condi tions immediately on a bed of solid carbon dioxide. Remove the water from the ampoules in a conventional freeze-drying apparatus, to a moisture limit not exceeding 1% and seal the ampoules under dry nitrogen. Store in a cool place, protected from light. The ampoules may be reconstituted immediately before use, by the addition of 2 ml. water for injection.

I claim:

1. The process for preparing a compound of the formula which comprises reacting a compound of the formula prising reacting griseofulvin with an alkali metal borohydride in an inert solvent medium. 2

References Cited UNITED STATES PATENTS 2,683,721 7/1954 Schlesinger et a1. 260343.3

OTHER REFERENCES Mulholland: J. Chem. Soc., London (1952), pp.- 3990 4 and 39978.

Gaylord: Reduction With Complex, Metal Hydrides (Interscience, 1956), pp. 24 to 26.

NICHOLAS S. RIZZO, Primary Examiner.

HENRY R. JILES, DONALD G. DAUS, Examiners. 

